Dental caries (terms “caries tooth, dental caries, and tooth caries, decayed teeth, etc.” mean the same disease; thus, these terms are abbreviated as “caries” hereinafter) is a disease caused by oral bacteria generating acids using sugars, particularly sucrose as a nutritious source to cause decalcification of teeth with the acids (the solubilization of inorganic components phosphoric acid and calcium from dental enamel and dentine with acids) and then decay teeth.
Various theories have been proposed about the detailed etiology of caries. Currently, it is understood that caries is initiated by the deposition of an insoluble, adhesive polysaccharide (insoluble glucan) generated by Streptococcus mutans (sometimes abbreviated as “S. mutans” hereinafter) on the dental surface. Specifically, insoluble glucan is generated from sucrose by bacteria such as Streptococcus mutans; the insoluble glucan deposits on dental surface to form dental plaque by oral bacteria and with food residues. Various microorganisms mainly including Streptococcus mutans can concurrently exist and proliferate in the dental plaque. Through the metabolism of these microorganisms, acids are generated; with the action of the acids, the pH is reduced to cause dental decalcification, leading to tooth decay and additionally to cause the occurrence and progress of caries.
Because caries occur due to the causes described above, one of preferable prophylactic approaches therefor is no intake of sugars causing the generation of insoluble glucan and acids by oral bacteria, such as sucrose. Because sucrose is abundantly contained in the natural kingdom and agricultural products such as fruits and vegetables and is an indispensable item in seasonings and foods for our daily dietary life, it is very hard to achieve no sucrose intake.
In such circumstances, so far, alternative sugars such as Xylitol (patent reference 1, patent reference 2), Palatinit (patent reference 3) and erythritol (non-patent reference 1) have been developed. The effects thereof on the prevention of acid generation and dental plaque formation with caries-inducing bacteria have been elucidated. Additionally, D-arabitol at a sweetness level of about 68% of the sweetness level of sucrose, D-allose at a sweetness level of about 65% of the sweetness level of sucrose and L-mannose at the same sweetness level as that of glucose have been proposed as non-cariogenic materials (patent reference 4). Furthermore, the use of a cyclic tetrose D-psicose as a material inducing a low level of caries has also been suggested (patent reference 5).
Still further, it has been known commonly that dental plaque not only causes decayed teeth but also causes periodontal diseases such as gingivitis and periodontitis (gumboil). Therefore, it is an important issue to suppress or kill etiologic bacteria causing caries or periodontal diseases, such as Streptococcus mutans, so as to prevent such various diseases. Accordingly, oral compositions with such effects have been desired strongly. So as to apply such compositions to the prophylaxis and therapeutic treatment of periodontal diseases, the alternative sugars disadvantageously have problematic safety profiles when used in the oral compositions; the alternative sugars are hardly blended in stable manners in such oral compositions; the alternative sugars disadvantageously affect flavor; the alternative sugars have insufficient effects; and the cost for blending the alternative sugars therein is problematic.    Patent reference 1: JP-A-2000-128752    Patent reference 2: JP-A-2000-53549    Patent reference 3: JP-A-2000-281550    Patent reference 4: JP-A-2000-68970    Patent reference 5: WO 01-090338    Non-patent reference 1: Kawanabe et al., Caries Res. 26 p. 358-362 (1992)